1 files changed, 21 insertions, 25 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index f7337d7bd45..523f5450564 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1628,32 +1628,28 @@ void DwarfDebug::beginFunction(const MachineFunction *MF) {
 void DwarfDebug::addScopeVariable(LexicalScope *LS, DbgVariable *Var) {
   SmallVectorImpl<DbgVariable *> &Vars = ScopeVariables[LS];
   DIVariable DV = Var->getVariable();
-  if (DV.getTag() == dwarf::DW_TAG_arg_variable) {
-    DISubprogram Ctxt(DV.getContext());
-    DIArray Variables = Ctxt.getVariables();
-    // If the variable is a parameter (arg_variable) and this is an optimized
-    // build (the subprogram has a 'variables' list) make sure we keep the
-    // parameters in order. Otherwise we would produce an incorrect function
-    // type with parameters out of order if function parameters were used out of
-    // order or unused (see the call to addScopeVariable in endFunction where
-    // the remaining unused variables (including parameters) are added).
-    if (unsigned NumVariables = Variables.getNumElements()) {
-      // Keep the parameters at the start of the variables list. Search through
-      // current variable list (Vars) and the full function variable list in
-      // lock-step looking for this parameter in the full list to find the
-      // insertion point.
-      SmallVectorImpl<DbgVariable *>::iterator I = Vars.begin();
-      unsigned j = 0;
-      while (I != Vars.end() && j != NumVariables &&
-             Variables.getElement(j) != DV &&
-             (*I)->getVariable().getTag() == dwarf::DW_TAG_arg_variable) {
-        if (Variables.getElement(j) == (*I)->getVariable())
-          ++I;
-        ++j;
-      }
-      Vars.insert(I, Var);
-      return;
+  // Variables with positive arg numbers are parameters.
+  if (unsigned ArgNum = DV.getArgNumber()) {
+    // Keep all parameters in order at the start of the variable list to ensure
+    // function types are correct (no out-of-order parameters)
+    //
+    // This could be improved by only doing it for optimized builds (unoptimized
+    // builds have the right order to begin with), searching from the back (this
+    // would catch the unoptimized case quickly), or doing a binary search
+    // rather than linear search.
+    SmallVectorImpl<DbgVariable *>::iterator I = Vars.begin();
+    while (I != Vars.end()) {
+      unsigned CurNum = (*I)->getVariable().getArgNumber();
+      // A local (non-parameter) variable has been found, insert immediately
+      // before it.
+      if (CurNum == 0)
+        break;
+      // A later indexed parameter has been found, insert immediately before it.
+      if (CurNum < ArgNum)
+        break;
     }
+    Vars.insert(I, Var);
+    return;
   }
 
   Vars.push_back(Var);